This invention pertains to the art of fluid flow regulation and more particularly to shutoff type flow valves. The invention is particularly applicable to a type of valve known as a pinch valve for use in a biotechnological environment. The pinch valve incorporates a flexible, substantially tubular member that is selectively compressed along an exterior portion to close a central flow passage and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other environments and applications.
Handling of biotechnological components requires an ultra-clean environment and special safeguards to minimize damage to biological material such as elongated chains. Specifically, a smooth, reliable shutoff arrangement is required and dependable drainability of the flow line is necessary to prevent entrapment of the biological material. Only certain types of materials may be utilized in the valve construction due to the potential for interaction with the biological material in the fluid.
Typically, pinch valves incorporate a flexible or elastomeric sleeve that is compressed along an exterior portion to selectively open and close a central fluid passage defined through the sleeve. The life cycle of such a flexible sleeve is dependent on the strength and wear characteristics of the elastomeric material. Particularly, closing the valve places the sleeve under tensile forces which, with repeated flexing or cycling, tends to become stretched and unusable.
For example, U.S. Pat. No. 3,350,053 to Schmitz, issued Oct. 31, 1967, describes some of the problems inherent with pinch valves utilized in the industry. One solution proposed in that patent to the repeated flexing of the elastomeric sleeve is to reduce the diameter to length ratio of the valve body and sleeve to as low a value as possible. It is believed that this ratio reduction provides a compact structure that limits the stretching of the resilient material of the sleeve.
Another avenue of attack for increasing the cycle life of the sleeve is to limit forces tending to pull end flanges of the sleeve toward the center of the valve. The solution offered by the Schmitz patent to this problem is to employ a preselected bulge molded into the sleeve between the end flanges. In this manner, the sleeve is positioned in an unstretched, slack arrangement and a valve actuating member has a predetermined range of movement that takes up the slack molded into the sleeve. Thus, the sleeve experiences reduced, if any, tensile forces as a result of actuator movement to a closed position. Although suitable for some fluid applications, it is considered desirable to eliminate the bulge molded into the sleeve in other applications because of the potential entrapment of biological material and variation in the flow passage configuration that disrupts the pursuit of laminar flow conditions.
Yet another problem associated with remotely operated valves of this type is the lack of any indication of the valve open and closed positions. It is critical to readily determine whether or not fluid flow is shut off so that downstream operations for repair, servicing, and the like may be conducted. Prior pinch valve structures have failed to adequately address this situation.
Still another area of concern is the drainability of the valve that may be effected through the type of actuation mechanism or repeated flexing of the valve sleeve. Although the elastomeric materials utilized in the makeup of the valve sleeve have resilient properties, continued flexing or cycling results in stretching or permanent deformation of the valve sleeve. If the sleeve is closed through the application of peripheral forces along a bottom portion of the sleeve as is common in prior pinch valve structures, stretching or deformation may result. This, in turn, inhibits drainability of the valve after the valve has been in use for an extended period of time since fluid upstream of the actuating area of the sleeve will not freely drain along the bottom portion.
As indicated above, some pinch valve arrangements utilize end flanges in an effort to grip the valve sleeve in the body. The use of flanges has met with substantial commercial success but the sleeve configuration has provided some difficulty in maintenance and replacement situations.
The necessity for an ultra-clean environment requires that components handling biological materials be frequently and thoroughly cleaned. For example, prior valves have been autoclaved, i.e., subject to sterilizing action using superheated steam under pressure. The entire valve body is heated during the sterilizing process, which heating can have adverse effects on the operation of the valve.
The subject invention contemplates a new and improved pinch valve arrangement that overcomes all of the above referenced problems and others and provides as easily assembled, reliable valve structure.